SOLUTION: Population ecology graph worksheet key - Studypool - Free Printable

Problem Analysis and Solution

The image provided shows a survivor graph with four different growth curves labeled A, B, C, and D. Each curve represents the percentage of survivors as a function of age. The task involves analyzing these curves and answering specific questions based on their characteristics.

#### Curves Description:
1. Curve A: Represents the life expectancy of white women in the USA during 1939-1941.
2. Curve B: Represents the life expectancy of women in India during 1921-1930.
3. Curve C: Represents a theoretical population where individuals have an equal chance of dying at any age (exponential decay).
4. Curve D: Represents a hypothetical scenario where individuals have a constant probability of survival until a certain age, after which survival drops sharply.

#### Questions and Solutions:

---

Question 1: Which has a steeper slope if compared to others? Why?

- Answer: Curve D has the steepest slope.
- Explanation:
- The steepness of a curve in a survivor graph indicates the rate at which the percentage of survivors decreases with age.
- Curve D shows a sharp decline in the percentage of survivors starting from a relatively young age (around 20 years). This indicates a high mortality rate early in life, followed by a plateau where the survival rate remains constant for a period before dropping sharply again.
- In contrast, Curves A, B, and C show more gradual declines, indicating lower mortality rates compared to Curve D.

---

Question 2: What is the half-life of Curve C?

- Answer: The half-life of Curve C is 10 years.
- Explanation:
- The half-life of a curve is the time it takes for the percentage of survivors to reduce to half of its initial value.
- Curve C is explicitly labeled as "Theoretical population with half-life of 10 yr," so the half-life is directly given as 10 years.

---

Question 3: If you were a fish, which curve would you choose to live? Why?

- Answer: Curve C.
- Explanation:
- Curve C represents a theoretical population where individuals have an equal chance of dying at any age. This means that the probability of surviving to any given age is consistent and does not increase or decrease significantly over time.
- For a fish, this would be an ideal scenario because it implies a stable and predictable survival pattern without a sudden drop in survival rates at any particular age.

---

Question 4: What is the life expectancy of Curve A? Explain.

- Answer: The life expectancy of Curve A is approximately 70 years.
- Explanation:
- Life expectancy can be estimated by finding the age at which the survivor curve reaches approximately 50% of its initial value (i.e., when half of the population has survived).
- From the graph, Curve A crosses the 50% mark around the age of 70 years. This indicates that the average life expectancy for white women in the USA during 1939-1941 was around 70 years.

---

Question 5: Why is Curve D placed to the right and just below Curve C?

- Answer: Curve D is placed to the right and just below Curve C because it represents a higher mortality rate early in life but stabilizes later.
- Explanation:
- Curve D starts with a very steep decline, indicating high mortality rates in early life. This is why it is positioned to the left of Curve C initially.
- After a certain age, Curve D levels off and remains relatively flat for a period, indicating a lower mortality rate compared to the initial phase. This is why it is positioned below Curve C but stabilizes later.
- The placement to the right reflects the fact that individuals who survive the initial high-mortality phase have a longer expected lifespan compared to the exponential decay represented by Curve C.

---

Final Answers:

1. Steepest slope: Curve D.
2. Half-life of Curve C: 10 years.
3. Preferred curve for a fish: Curve C.
4. Life expectancy of Curve A: Approximately 70 years.
5. Placement of Curve D: Due to higher early mortality and stabilization later.

Boxed Final Answer:
\[
\boxed{1. \text{Curve D}, 2. 10 \text{ years}, 3. \text{Curve C}, 4. \text{Approximately 70 years}, 5. \text{Higher early mortality and stabilization later}}
\]